ADVANCEMENTS IN SYNTHETIC APERTURE RADAR (SAR) TECHNIQUES FOR GLACIER VELOCITY MEASUREMENT

Monitoring glacier velocity constantly is vital because it provides information on how glacier flow dynamics respond to climate change.Glacier velocity also significantly influences the determination of glacier mass balance and ice thickness.Differential SAR Interferometry (DInSAR) uses SAR images to measure very small surface motions with good resolution over large swaths.This article reviews advancements in SAR techniques for glacier velocity estimation.Various DInSAR approaches, from the conventional to the advanced ones, have been discussed.The three-pass and four-pass DInSAR methods require more SAR images but reduce the Digital Elevation Model (DEM) induced error as compared to the two-pass method.Advanced DInSAR approaches such as Persistent Scatterer Interferometry (PSI), Small Baseline Subset (SBAS), Multiple Aperture Interferometry (MAI) allow to examine the temporal evolution of glacier deformations.Offset tracking methods with their capability of determining both the slant range and azimuth components of glacier motion have also been discussed.The DInSAR approach is more suitable for slow-moving glaciers while Offset tracking excels in fast-moving glaciers.Both methods complement each other and one can obtain the best result by integrating both techniques.